60ml bottle of Platinum Carbon Black fountain pen ink. This is slightly different than conventional fountain pen ink, because it is pigmented instead of dye-based. This makes it very permanent and lightfast, though it does require more diligent maintenance in your fountain pen. It's ideal for brush pens and fountain pens being used on paper where you need ink to dry on the surface instead of soaking in.
This waterproof, pigment-based carbon ink is highly regarded by artists, and is a standard for ink-washing and mixed media work where you need to draw a line that will later be washed overtop.
Caution: Pigmented inks are intended for use in fountain pens, though they require more diligent maintenance and should not be left to dry out in a pen. It is best to clean it from your pen at least once a week to prevent clogging. Certain pens may handle pigmented inks better than others.